The present invention relates to an apparatus for the replacement of underground pipe.
Underground pipes are subject to inevitable deterioration and wear and, therefore, must be replaced from time to time. An obvious method for replacing existing underground pipe with replacement pipe is to excavate the entire length of the existing pipe, remove it and place new replacement pipe into the excavation. Excavation of existing pipe is time-consuming, labor-intensive and results in damage to the area surrounding the excavation. In many instances pipes often lie beneath driveways, buildings, or gardens, and property owners are very concerned about any damage that may result thereto. In addition, excavation is often made difficult by the presence of underground utilities.
Accordingly, it is an object of the present invention to provide an apparatus and method for replacing underground pipe requiring minimal excavation.
Other devices and methods have previously been proposed for use in replacement of underground pipes and mains. For example, those disclosed in U.S. Pat. No. 6,171,026 issued to Crane et al.; U.S. Pat. No. 6,092,553 issued to Hodgson; U.S. Pat. No. 5,544,977 issued to Crane et al.; U.S. Pat. Nos. 4,720,211; and 4,738,565 issued to Streatfield et al. However, all of the devices and methods disclosed by the above patents suffer from several drawbacks.
The devices and methods disclosed by the prior are drawn through an existing pipe by a cable, chain or similar pulling means. Due to the forces involved in the operation of such devices the pulling means may break from time to time, thereby leaving the device lodged in the ground. Similarly, the device may become lodged if it encounters an obstruction which prevents it for being advanced. In such situations the existing underground pipe is blocked and damaged and the only remedy is to retrieve the device by excavation. Such excavation results in significant additional expenditures of time and money and nullifies the advantages of trenchless pipe replacement. In many instances, excavation is not an acceptable alternative to the customer. Accordingly, it is an object of the present invention to provide an improved device for trenchless underground pipe replacement, which is easily retrieved without further excavation.
In addition, the use of the devices and methods disclosed by the prior art blocks the existing underground pipe such that fluids carried by the pipe cannot pass. Accordingly, it is an object of the present invention to provide a device for the trenchless replacement of underground pipe that permits the passage of fluids through the existing underground pipe as the device is drawn through the existing underground pipe.
The prior art additionally discloses devices and methods for drawing sections of new pipe into the cavity of the existing underground pipe. Due to the forces involved in drawing new sections of pipe through such a cavity only certain types of replacement pipe can be used. The type of replacement pipe is limited by the strength of the joints between adjoining sections of replacement pipe. Such joints must be strong enough to draw a plurality of sections of replacement pipe through the cavity of the existing underground pipe. Accordingly, it is an objective of the present invention to provide a device for the trenchless replacement of underground pipe that permits existing underground pipe to be replaced with a wide variety of replacement pipes.
The devices and methods for the trenchless replacement of underground pipe disclosed by the prior art involve the use of relatively long and rigid tools, which cannot follow turns or bends of the existing underground pipe. Accordingly, it is a further objective of the present invention to provide a device for the trenchless replacement of underground pipe which can pass through a bend or turn of an existing underground pipe of up to 45xc2x0 or more.
Some of the devices disclosed by the prior art, for example that described by U.S. Pat. No. 4,720,211, issued to Streatfield et al., are designed to fracture the existing underground pipe to make way for new pipe. However, when subjected to such devices some types of polymeric pipes tend to stretch or expand and are therefore not fracturable. Such polymeric pipes must be cut in order to make way for new pipe. Accordingly, it is an object of the present invention to provide a device that cuts existing underground pipe.
An apparatus and method are provided for the trenchless replacement of underground pipes, wherein a tool is drawn through an existing underground pipe. The tool includes several subsections; a first subsection cuts or fractures the existing underground pipe as it is drawn through the existing underground pipe, a second subsection causes some outward movement of the fragments of the existing underground pipe and causes a widening of the cavity of the existing underground pipe, and a third subsection guides replacement pipe into the cavity of the existing underground pipe. The subsections are engageable with one another to the tool. The first subsection is engaged with the second subsection and the second subsection is engaged with the third subsection. Each of the subsections has a longitudinal bore extending therethrough such that when the subsections are engaged the tool has a longitudinal bore extending from the front end of the first subsection to the rear end of the third subsection. The tool additionally comprises a block, which is engageable with the bore. A first line for pulling the tool forward is passed through the bore and connected to the block. A second line for retrieving the block is also connected to the block.
The pulling line is connected to any of a variety of devices capable of generating sufficient force to draw the pulling line, the tool and sections of replacement pipe through the existing underground pipe. For example the pulling line may be connected to a hydraulic cylinder supported on a frame. The action of the hydraulic cylinder draws the pulling line, tool and sections of replacement pipe into the existing underground pipe.
In one aspect of the present invention the tool is divided into subsections. The subsections of the tool may be functionally distinct, such that one subsection cuts or fractures the existing underground pipe, another widens the cavity, and another draws replacement pipe into place.
Alternatively, subsections of the tool may combine more than one functional element, for example one subsection of the tool may both fracture the existing underground pipe and widen the cavity. The subsections of the tool are capable of movement relative to one another as the tool is drawn through the existing underground pipe. Such movement allows the tool to articulate or bend as it is drawn through an existing underground pipe. This aspect of the invention allows the tool to be drawn through curves or changes in direction of the existing underground pipe.
In another aspect of the present invention the tool has a longitudinal bore. The bore is sufficiently wide to allow the passage of a pulling line, or other pulling means, capable of drawing the tool through the existing underground pipe. The pulling line is passed through the existing underground pipe, through the bore of the tool and is connected to a large block. The large block is of a size and shape such that it cannot pass through the bore. Therefore when tension is applied to the pulling line, the large block is forced against the bore and the tool is forced through the existing underground pipe, thereby fracturing or cutting it, expanding the cavity and moving replacement pipe into the cavity.
The bore imparts several advantages to the tool over the prior art. The bore results in a lighter tool that is therefore easier to handle. In addition, the bore allows fluids carried by the existing underground pipe to pass through the tool while it is in use.
Devices for the replacement of underground pipe that are drawn through existing underground pipe from time to time encounter obstructions. In the event of such an obstruction, the bore of the tool of the present invention allows the tool to be retrieved from the existing underground pipe without additional excavation. By pulling on the retaining line, the large block and pulling line may be withdrawn from the underground pipe while leaving the tool and replacement pipe in situ. The large block may then be disconnected from the pulling line. The large block and retaining line are then moved to an excavation ahead of the obstruction and tool from which the pulling line and tool were initially drawn through the existing underground pipe. There the large block is reconnected to the pulling line and drawn through the existing underground pipe in the other direction. When the large block meets the tool, the tool and replacement pipe are forced back through the cavity of the existing underground pipe so that they may be retrieved. The tool and replacement pipe may then be drawn through the existing underground pipe in the other direction.
In the event that the pulling line breaks during the operation of the tool, the tool and replacement pipe become lodged in the cavity of the existing underground pipe. However, the pulling line, retaining line and large block may then be withdrawn from the cavity of the existing underground pipe. Any of several methods may be used to feed a line through the existing pipe, tool and replacement pipe. For example a wire may be inserted from one end until it exits the other end. The wire is then used to draw the retaining line through the existing underground pipe, which in turn is used to draw a new pulling line and large block into the existing underground pipe. The tool and replacement pipe may then drawn through the existing underground pipe again or may be removed by forcing them back through the cavity of the existing underground pipe.
In another aspect of the invention, the tool is divided into subsections, which are easily separated from one another. This aspect, in conjunction with the bore of the tool, confers a further advantage over the prior art. When the tool encounters an obstruction, the retaining line, large block and pulling line may be withdrawn and the large block replaced with a small block. The small block is of a size and shape such that it can pass through the bore of the hindmost subsection(s) of the tool but cannot pass through the bore of the foremost subsection of the tool. The foremost subsection of the tool comprises a cutting or fracturing element and/or an expanding element of the tool. The pulling line, small block and retaining line are drawn into the cavity of the existing underground pipe until the small block contacts the bore of the foremost subsection of the tool. The small block then forces the foremost subsection of the tool through the existing underground pipe in order to clear the obstruction, fracture or cut the existing underground, and/or expand the cavity of the existing underground pipe. The pulling line, small block and retaining line can then be drawn back through the cavity of the existing underground pipe. The small block is disconnected from the pulling and retaining lines and the large block reconnected thereto. The pulling line, large block and retaining line are then drawn through the cavity of the existing underground pipe until the large block contacts the hindmost subsection of the of the tool. The obstruction having been cleared, the tool is forced through the cavity of the existing underground pipe, expanding it and moving replacement pipe into place.
In another aspect of the invention the replacement pipe is pushed into the cavity of the existing underground pipe. The hindmost subsection of the tool is a pipe guide that receives the first section of replacement pipe and guides the replacement pipe as the tool advances along the existing underground pipe. The retaining line passes from the tool through the sections of replacement pipe and exits the replacement pipe at the point where the new sections of replacement pipe are connected to those sections already in the cavity of the existing underground pipe. At the point where the retaining line exits the replacement pipe a plate is attached to the retaining line. As the pulling line is drawn through the existing underground pipe the tool and retaining line are drawn by the pulling line. The plate attached to the retaining line forces the sections of replacement pipe ahead as the retaining line advances through the existing underground pipe. In this manner the replacement pipe is pushed into the cavity of the existing underground pipe. The plate is removed periodically to connect an additional section of replacement pipe to those sections already in the cavity of the existing underground pipe. The plate is then reattached to the retaining line to force the replacement pipe into the cavity of the existing underground pipe. It is obvious to anyone skilled in the art that any of a variety of devices may be used in place of a plate to push the replacement pipe. An advantage of pushing the replacement pipe into place is that one need not wait for the bond between adjacent sections of replacement pipe to set before advancing the tool and replacement pipe through the existing underground pipe.
A further advantage of pushing replacement pipe into place is that less stress is placed on the joints between adjacent sections of replacement pipe than if the replacement pipe is pulled into place. Since bonds between adjacent sections of different types of replacement pipe vary in strength and set time, pushing the replacement pipe means that a wider variety of replacement pipes may be used.